Alan Kehew - Academia.edu (original) (raw)

Papers by Alan Kehew

Canadian Journal of Earth Sciences, 1994

The Watrous spillway was rapidly incised during a short-lived outburst from glacial Lake Elstow. ... more The Watrous spillway was rapidly incised during a short-lived outburst from glacial Lake Elstow. In its outlet area, the bed of Lake Elstow was composed of stagnant ice. The 40 km long spillway is incised across a divide, and terminates in the glacial Last Mountain Lake basin, where a coarse-grained fan, herein named the Little Manitou fan, was deposited. Clast sizes fine systematically from the mouth of the spillway across the surface of the fan, from boulders with a maximum mean intermediate diameter of 1.26 m to cobbles, over a distance of 7 km on the south lobe of the fan. Large clasts are concentrated on the surface, and probably represent deposition at peak discharge. The proximal margin of the south lobe of the fan is hummocky, suggesting that deposition of sediment at its apex was on stagnant ice with subsequent collapse. Paleovelocity, paleodischarge, and other parameters were estimated for the outburst flood using a critical shear stress approach. These approaches yielded ...

Environmental Earth …, 2011

... Redox evolution in glacial drift aquifers: role of diamicton units in reduction of Fe(III) Na... more ... Redox evolution in glacial drift aquifers: role of diamicton units in reduction of Fe(III) Nathaniel A. Barnes • Alan E. Kehew • RV Krishnamurthy • Carla M. Koretsky Received: 5 December 2009 / Accepted: 13 May 2010 / Published online: 8 June 2010 © Springer-Verlag 2010 ...

Global and Planetary Change, 2010

The Wadi Isla drainage basin, a narrow steep bedrock canyon and its tributaries, rises near the h... more The Wadi Isla drainage basin, a narrow steep bedrock canyon and its tributaries, rises near the highest elevations of the Precambrian Sinai massif on the eastern margin of the tectonically active Gulf of Suez rift. The basin area upstream from the mountain front is 191km2 and downstream the wadi crosses a broad alluvial plain to the Red Sea. Stream-transported boulders

The isotopic composition of modern precipitation (from IAEA stations) over North Africa is genera... more The isotopic composition of modern precipitation (from IAEA stations) over North Africa is generally enriched (e.g., average δD ± 1δ: Algeria: - 17.05‰ ± 8.81; Tunisia: -24.2‰ ± 4.23; Libya: -17.7‰ ± 2.72; Egypt: -15.46‰ ± 3.45) compared to fossil groundwater across North Africa that is progressively depleted from west to east (e.g., Morocco: δD = -20 to -30‰; Algeria δD = -30 to -50‰; Egypt δD = -72 to -81‰) suggesting that precipitation during previous wet climatic periods (450,000 yr B.P to 10,000 yr B.P) resulted from wind regimes different from those prevailing nowadays. A few exceptions to the modern isotopic values were noted from the IAEA stations in Egypt, where the average δD values for five months (March 1982, December 1987, December 1991, March 2002 and April 2002) collected from Sidi Barrani, Cairo, Rafah, and El-Arish IAEA stations all showed isotopic depletions (δD = -43.7‰, to -56‰) similar to those of the fossil waters in the Western and Eastern Deserts of Egypt. Th...

A hydrogeochemical survey involving collection and analysis of 51 well, spring and stream water s... more A hydrogeochemical survey involving collection and analysis of 51 well, spring and stream water samples from an area of about 216 km2 was carried out over a part of the Arabo-Nubian Shield of southern Sinai (locally known as St. Catherine area). The distribution and relationships of major and trace constituents of water with sulphide occurrences were described. Only six major chemical parameters, including high electric conductivity, Ca, Mg, SO4, Cl and low HCO3 contents, can be used as prospecting guides in the search for sulphide minerals. Trace element anomalies, including Fe, Pb. Cr, and Mn, are distributed over, the mineralized zones owing to their relative immobility in this arid environment. On the other hand, the relatively mobile elements; including Cu, Mo, Ni and Zn; are significantly increased in waters as the distance increased away from the mineralized zone. As a result of the present research, two hydrogeochemical anomalies were delineated; those suggest the presence o...

Palaeogeography, Palaeoclimatology, Palaeoecology, 2012

Quaternary International, 2012

The surficial terrain of the Saginaw Lobe in southern Michigan is divided into 4 landsystems, num... more The surficial terrain of the Saginaw Lobe in southern Michigan is divided into 4 landsystems, numbered sequentially from southwest to northeast, containing related assemblages of sediments and landforms, two of which appear to have a genetic relationship with the bedrock units over which they lie. Landsystem 1 consists of the Sturgis Moraine, a terminal/recessional moraine, and an adjacent drumlin field. The moraine is a high-relief ridge with hummocky topography and ice-walled lake plains at its crest, and thick, coarse outwash fans on its distal margin. The drumlin field extends up-glacier from the Sturgis Moraine across the subcrop of the Mississippian Coldwater Shale to the subcrop of the overlying Marshall Sandstone. The low permeability of the shale may have increased basal pore pressures into a range in which deformation of basal sediment into drumlins occurred. Landsystem 2 overlies the subcrop of the Marshall Sandstone. Stagnation of the lobe behind a discontinuous moraine in this area is indicated by high relief, collapse topography, composed of kames, eskers, and ice-walled lake plains. A system of tunnel valleys terminates and merges in this landsystem with large outwash fans and plains sloping away from the margin. High basal drainage into the sandstone may have facilitated stagnation across a broad area to form this landsystem. Landsystem 3 may have also developed during stagnation of the lobe, but it differs from landsystem 2 by its more subdued relief. It contains a network of evenly spaced, southwest-trending open tunnel valleys that contain discontinuous esker segments. Landsystem 4 consists of till plains and low recessional moraines formed as the Saginaw Lobe retreated downslope into Saginaw Bay of the Lake Huron Basin. Tunnel valleys are absent in this area.

Environmental Earth Sciences, 2009

A back propagation artificial neural network approach is applied to three common challenges in en... more A back propagation artificial neural network approach is applied to three common challenges in engineering geology: (1) characterization of subsurface geometry/position of the slip (or failure surface) of active landslides, (2) assessment of slope displacements based on ground water elevation and climate, and (3) assessment of groundwater elevations based on climate data. Series of neural network models are trained, validated,

Proceedings of the First …, 2007

... by Chase et al. (2001b), the stratigraphic units visible in a shore-parallel profile are as f... more ... by Chase et al. (2001b), the stratigraphic units visible in a shore-parallel profile are as follows (Figure 2): Figure 2. Longshore stratigraphic profile of the coastal bluff in the study area and the location of the Miami Park South study site. Vertical exaggeration is 50x. Lower clay-...

Quaternary Science Reviews, 2005

Geomorphic evidence and stratigraphic information from boreholes suggest that the oversized Centr... more Geomorphic evidence and stratigraphic information from boreholes suggest that the oversized Central Kalamazoo River Valley (CKRV) in southwest Michigan resulted from a catastrophic outburst flood emanating from subglacial channels under the Saginaw lobe of the Laurentide Ice Sheet. The CKRV occurs as a deeply incised trench over 2 km wide and in excess of 50 m deep situated in a reentrant formed by the Lake Michigan, Saginaw and Huron-Erie lobes.

Quaternary Science Reviews, 2005

The dynamics of the late Wisconsin Lake Michigan Lobe of the Laurentide Ice Sheet, as interpreted... more The dynamics of the late Wisconsin Lake Michigan Lobe of the Laurentide Ice Sheet, as interpreted by sediment-landform assemblages along its southeastern margin, are consistent with fast flow driven by high subglacial pore pressures. A major advance of the Lake Michigan Lobe terminated at the Kalamazoo Moraine, where proglacial glaciotectonic activity, marginal stagnation, and release of subglacial meltwater marked the extent of the advance. A large portion of the Valparaiso ''Moraine'', west of the Kalamazoo Moraine, is actually a drumlinized, till-capped upland plain rather than an ice-marginal landform assemblage. Lacustrine sediment, underlying the surficial diamicton in the Valparaiso upland, is glaciotectonically deformed to a depth of 10 m. The deformed interval consists of folded sandy and silty lacustrine sediment, which is in places sharply truncated by the overlying diamicton. Decoupling of the glacier from its bed is suggested by a discontinous thin bed of sand at the base of the diamicton, and by the sharp truncation of deformed lacustrine sediment. The association of drumlins, proglacial and subglacial deformation, marginal stagnation, and major ice-marginal outwash-fan deposition are indicative of fast flow, perhaps in a surge. These characteristics are consistent with a terrestrial ice-stream model for the Lake Michigan Lobe. r

Global and Planetary Change, 2010

The Wadi Isla drainage basin, a narrow steep bedrock canyon and its tributaries, rises near the h... more The Wadi Isla drainage basin, a narrow steep bedrock canyon and its tributaries, rises near the highest elevations of the Precambrian Sinai massif on the eastern margin of the tectonically active Gulf of Suez rift. The basin area upstream from the mountain front is 191 km 2 and downstream the wadi crosses a broad alluvial plain to the Red Sea. Stream-transported boulders within the lower canyon (up to 5 m in diameter) and in a fan downstream indicate extremely high competence. In one reach, a 60-m-long boulder berm, ranging in height from 3 to 4 m, lies along the southern wall of the canyon and contains boulders 2-3 m in diameter. Boulder deposits beyond the mouth of the canyon generally appear to be less than several metres thick and are composed of imbricated, wellsorted boulders. The last flood that deposited these boulders is believed to have been a debris torrent with a low content of fines. Mean intermediate diameter decreases from about 1.5 m just beyond the mouth of the canyon, where the channel width expands to 300 m, to about 0.5 m downstream to the point at which the valley is no longer confined on its south side. Using the empirical formula of Costa (1983), these clasts represent velocities decreasing from about 6.5 m s − 1 to 3.7 m s − 1 . Flood velocity and discharge were also calculated within the canyon, using , Costa's (1983) method and by the Manning equation. Parameters for the calculation include a channel width of 65 m, flow depth of 3.5 m (average height of the boulder berm), an average slope of 0.038 and a roughness coefficient of 0.06. The resulting values include a velocity range between 6.8 m s − 1 and 7.3 m s 1 and a corresponding discharge range of ∼1550 m 3 s − 1 to 1660 m 3 s − 1 . A lower limiting discharge of 1320 m 3 s − 1 was obtained with an assumption of critical flow conditions. The boulder fan is much coarser than the older alluvial plain sediment, suggesting an increase in flood magnitudes in more recent timesperhaps in response to renewed uplift of the mountain front and/or climate change. A calibrated rainfall-runoff model was developed using SWAT to estimate modern flood discharges in Wadi Isla. The magnitude of discharge from 1998-2006 did not exceed 500 m 3 s − 1 . Artificial precipitation amounts (90 and 150 mm) were used to extrapolate from recent rainfall amounts to the amount of rainfall needed to produce a discharge range of 1320 m 3 s − 1 to 1660 m 3 s − 1 . Results show that rainfall must range between ∼102 mm and 125 mm to produce this discharge.

Geological Society of America Bulletin, 1987

Glacial-lake outbursts occurred in the northern Great Plains as ice-marginal lakes suddenly drain... more Glacial-lake outbursts occurred in the northern Great Plains as ice-marginal lakes suddenly drained, forming an interconnected system of glacial-lake spillways. The outbursts were highly erosive, and consequently, deposits from such discharges are rare in the spillways. ...

Environmental and Engineering Geoscience, 2007

... Evans, SG, 2002, Contrasting failure behavior of two large landslides in silt and clay: Canad... more ... Evans, SG, 2002, Contrasting failure behavior of two large landslides in silt and clay: Canadian Geotechnical Journal, 39. 46-62. GeoRef. ↵ Griffiths, DV, and Lane, PA, 1999, Slope stability analysis by finite elements: Geotechnique, 49, 3. 387-403. ... Glynn, ME, Chase, RB, and ...

Environmental and Engineering Geoscience, 2008

... the cross-section balancing method produces geometrically permissible results, it is highly i... more ... the cross-section balancing method produces geometrically permissible results, it is highly intuitive and extremely time consuming, especially when dealing with multiple blocks (Chase et al ... The oldest and simplest approach is polynomial interpolation (Kincaid and Cheney, 2002 ...

Boreas, 2013

ABSTRACT Tunnel valleys are common throughout the terrain of the Saginaw Lobe of the Laurentide I... more ABSTRACT Tunnel valleys are common throughout the terrain of the Saginaw Lobe of the Laurentide Ice Sheet in southern Michigan. The set of valleys described in this paper is regularly spaced in a radial pattern behind the Kalamazoo Moraine, an ice-marginal position formed during retreat from the Last Glacial Maximum. These valleys are divided into proximal and distal groups lying north and south, respectively, of a major river valley that cross-cuts the tunnel valleys at right angles. Based on a series of rotasonic borings and core analysis, the proximal valleys are shallow, contain minimal sediment fill, and overlie fine-grained diamicton and glaciolacustrine sediment, whereas the distal valleys are deeply incised into the substrate and are partially filled with coarse sediment. The distal valleys terminate within a broad zone of high-relief, hummocky topography representing stagnation and collapse behind the Kalamazoo ice margin. The proximal valleys occur within a more subdued landscape located farther from the ice margin. Although some elements of existing genetic models are consistent with these valleys, none appears to be completely compatible with their stratigraphy and morphology. Initial incision of the valleys could have involved short-lived moderate- to high-discharge flows, followed by deposition during or after the events. The deep incision and thick, coarse sediment in distal valleys in the stagnant marginal zone probably involved supraglacial meltwater draining to the bed as the margin downwasted. Fining-upward eskers inset into the valleys were formed by flows of declining energy in small late-stage conduits.

ABSTRACT The stable oxygen and hydrogen isotopic composition of fossil groundwater (>30k y... more ABSTRACT The stable oxygen and hydrogen isotopic composition of fossil groundwater (>30k yrs B.P.) over North Africa is progressively depleted from west to east (e.g., average δ18O: Morocco: –6.4‰; Algeria: –8.01‰; Tunisia: –8.38‰; Libya: –8.56‰; and Egypt: –10.98‰) compared to the modern precipitation (e.g., average δ18O ± 1δ: Morocco: –5.46‰ ± 1.22‰; Algeria: –3.9‰ ± 1.19‰; Tunisia: –4.67‰ ± 0.54‰; Libya: –3.8‰ ± 0.44‰; and Egypt: –3.96‰ ± 0.54‰) suggesting that the precipitation during the previous wet climatic periods (450,000 yr B.P to 10,000 yr B.P) resulted from wind regimes different from those prevailing today. The isotopic composition of fossil ground water can be used as a proxy for the isotopic composition of the paleo-precipitation recharging those ground waters with the Atlantic Ocean providing the source of moisture for recharging waters over Northern Africa. Based on this premise, a simple box model can be considered to model the paleo-precipitation to follow a simple Rayleigh distillation. Such a model shows that the reduction vapor factor was up to 30% by the time the moisture bearing air masses reached what is modern day Egypt. This model will be compared with available precipitation data for present day North African sites to constrain atmospheric processes that operated during the Pleistocene over Northern Africa that were responsible for the formation of the fossil aquifers (e.g. Nubian Aquifer) with depleted isotopic ratios.

Canadian Journal of Earth Sciences, 1994

The Watrous spillway was rapidly incised during a short-lived outburst from glacial Lake Elstow. ... more The Watrous spillway was rapidly incised during a short-lived outburst from glacial Lake Elstow. In its outlet area, the bed of Lake Elstow was composed of stagnant ice. The 40 km long spillway is incised across a divide, and terminates in the glacial Last Mountain Lake basin, where a coarse-grained fan, herein named the Little Manitou fan, was deposited. Clast sizes fine systematically from the mouth of the spillway across the surface of the fan, from boulders with a maximum mean intermediate diameter of 1.26 m to cobbles, over a distance of 7 km on the south lobe of the fan. Large clasts are concentrated on the surface, and probably represent deposition at peak discharge. The proximal margin of the south lobe of the fan is hummocky, suggesting that deposition of sediment at its apex was on stagnant ice with subsequent collapse. Paleovelocity, paleodischarge, and other parameters were estimated for the outburst flood using a critical shear stress approach. These approaches yielded ...

Environmental Earth …, 2011

... Redox evolution in glacial drift aquifers: role of diamicton units in reduction of Fe(III) Na... more ... Redox evolution in glacial drift aquifers: role of diamicton units in reduction of Fe(III) Nathaniel A. Barnes • Alan E. Kehew • RV Krishnamurthy • Carla M. Koretsky Received: 5 December 2009 / Accepted: 13 May 2010 / Published online: 8 June 2010 © Springer-Verlag 2010 ...

Global and Planetary Change, 2010

The Wadi Isla drainage basin, a narrow steep bedrock canyon and its tributaries, rises near the h... more The Wadi Isla drainage basin, a narrow steep bedrock canyon and its tributaries, rises near the highest elevations of the Precambrian Sinai massif on the eastern margin of the tectonically active Gulf of Suez rift. The basin area upstream from the mountain front is 191km2 and downstream the wadi crosses a broad alluvial plain to the Red Sea. Stream-transported boulders

The isotopic composition of modern precipitation (from IAEA stations) over North Africa is genera... more The isotopic composition of modern precipitation (from IAEA stations) over North Africa is generally enriched (e.g., average δD ± 1δ: Algeria: - 17.05‰ ± 8.81; Tunisia: -24.2‰ ± 4.23; Libya: -17.7‰ ± 2.72; Egypt: -15.46‰ ± 3.45) compared to fossil groundwater across North Africa that is progressively depleted from west to east (e.g., Morocco: δD = -20 to -30‰; Algeria δD = -30 to -50‰; Egypt δD = -72 to -81‰) suggesting that precipitation during previous wet climatic periods (450,000 yr B.P to 10,000 yr B.P) resulted from wind regimes different from those prevailing nowadays. A few exceptions to the modern isotopic values were noted from the IAEA stations in Egypt, where the average δD values for five months (March 1982, December 1987, December 1991, March 2002 and April 2002) collected from Sidi Barrani, Cairo, Rafah, and El-Arish IAEA stations all showed isotopic depletions (δD = -43.7‰, to -56‰) similar to those of the fossil waters in the Western and Eastern Deserts of Egypt. Th...

A hydrogeochemical survey involving collection and analysis of 51 well, spring and stream water s... more A hydrogeochemical survey involving collection and analysis of 51 well, spring and stream water samples from an area of about 216 km2 was carried out over a part of the Arabo-Nubian Shield of southern Sinai (locally known as St. Catherine area). The distribution and relationships of major and trace constituents of water with sulphide occurrences were described. Only six major chemical parameters, including high electric conductivity, Ca, Mg, SO4, Cl and low HCO3 contents, can be used as prospecting guides in the search for sulphide minerals. Trace element anomalies, including Fe, Pb. Cr, and Mn, are distributed over, the mineralized zones owing to their relative immobility in this arid environment. On the other hand, the relatively mobile elements; including Cu, Mo, Ni and Zn; are significantly increased in waters as the distance increased away from the mineralized zone. As a result of the present research, two hydrogeochemical anomalies were delineated; those suggest the presence o...

Palaeogeography, Palaeoclimatology, Palaeoecology, 2012

Quaternary International, 2012

The surficial terrain of the Saginaw Lobe in southern Michigan is divided into 4 landsystems, num... more The surficial terrain of the Saginaw Lobe in southern Michigan is divided into 4 landsystems, numbered sequentially from southwest to northeast, containing related assemblages of sediments and landforms, two of which appear to have a genetic relationship with the bedrock units over which they lie. Landsystem 1 consists of the Sturgis Moraine, a terminal/recessional moraine, and an adjacent drumlin field. The moraine is a high-relief ridge with hummocky topography and ice-walled lake plains at its crest, and thick, coarse outwash fans on its distal margin. The drumlin field extends up-glacier from the Sturgis Moraine across the subcrop of the Mississippian Coldwater Shale to the subcrop of the overlying Marshall Sandstone. The low permeability of the shale may have increased basal pore pressures into a range in which deformation of basal sediment into drumlins occurred. Landsystem 2 overlies the subcrop of the Marshall Sandstone. Stagnation of the lobe behind a discontinuous moraine in this area is indicated by high relief, collapse topography, composed of kames, eskers, and ice-walled lake plains. A system of tunnel valleys terminates and merges in this landsystem with large outwash fans and plains sloping away from the margin. High basal drainage into the sandstone may have facilitated stagnation across a broad area to form this landsystem. Landsystem 3 may have also developed during stagnation of the lobe, but it differs from landsystem 2 by its more subdued relief. It contains a network of evenly spaced, southwest-trending open tunnel valleys that contain discontinuous esker segments. Landsystem 4 consists of till plains and low recessional moraines formed as the Saginaw Lobe retreated downslope into Saginaw Bay of the Lake Huron Basin. Tunnel valleys are absent in this area.

Environmental Earth Sciences, 2009

A back propagation artificial neural network approach is applied to three common challenges in en... more A back propagation artificial neural network approach is applied to three common challenges in engineering geology: (1) characterization of subsurface geometry/position of the slip (or failure surface) of active landslides, (2) assessment of slope displacements based on ground water elevation and climate, and (3) assessment of groundwater elevations based on climate data. Series of neural network models are trained, validated,

Proceedings of the First …, 2007

... by Chase et al. (2001b), the stratigraphic units visible in a shore-parallel profile are as f... more ... by Chase et al. (2001b), the stratigraphic units visible in a shore-parallel profile are as follows (Figure 2): Figure 2. Longshore stratigraphic profile of the coastal bluff in the study area and the location of the Miami Park South study site. Vertical exaggeration is 50x. Lower clay-...

Quaternary Science Reviews, 2005

Geomorphic evidence and stratigraphic information from boreholes suggest that the oversized Centr... more Geomorphic evidence and stratigraphic information from boreholes suggest that the oversized Central Kalamazoo River Valley (CKRV) in southwest Michigan resulted from a catastrophic outburst flood emanating from subglacial channels under the Saginaw lobe of the Laurentide Ice Sheet. The CKRV occurs as a deeply incised trench over 2 km wide and in excess of 50 m deep situated in a reentrant formed by the Lake Michigan, Saginaw and Huron-Erie lobes.

Quaternary Science Reviews, 2005

The dynamics of the late Wisconsin Lake Michigan Lobe of the Laurentide Ice Sheet, as interpreted... more The dynamics of the late Wisconsin Lake Michigan Lobe of the Laurentide Ice Sheet, as interpreted by sediment-landform assemblages along its southeastern margin, are consistent with fast flow driven by high subglacial pore pressures. A major advance of the Lake Michigan Lobe terminated at the Kalamazoo Moraine, where proglacial glaciotectonic activity, marginal stagnation, and release of subglacial meltwater marked the extent of the advance. A large portion of the Valparaiso ''Moraine'', west of the Kalamazoo Moraine, is actually a drumlinized, till-capped upland plain rather than an ice-marginal landform assemblage. Lacustrine sediment, underlying the surficial diamicton in the Valparaiso upland, is glaciotectonically deformed to a depth of 10 m. The deformed interval consists of folded sandy and silty lacustrine sediment, which is in places sharply truncated by the overlying diamicton. Decoupling of the glacier from its bed is suggested by a discontinous thin bed of sand at the base of the diamicton, and by the sharp truncation of deformed lacustrine sediment. The association of drumlins, proglacial and subglacial deformation, marginal stagnation, and major ice-marginal outwash-fan deposition are indicative of fast flow, perhaps in a surge. These characteristics are consistent with a terrestrial ice-stream model for the Lake Michigan Lobe. r

Global and Planetary Change, 2010

The Wadi Isla drainage basin, a narrow steep bedrock canyon and its tributaries, rises near the h... more The Wadi Isla drainage basin, a narrow steep bedrock canyon and its tributaries, rises near the highest elevations of the Precambrian Sinai massif on the eastern margin of the tectonically active Gulf of Suez rift. The basin area upstream from the mountain front is 191 km 2 and downstream the wadi crosses a broad alluvial plain to the Red Sea. Stream-transported boulders within the lower canyon (up to 5 m in diameter) and in a fan downstream indicate extremely high competence. In one reach, a 60-m-long boulder berm, ranging in height from 3 to 4 m, lies along the southern wall of the canyon and contains boulders 2-3 m in diameter. Boulder deposits beyond the mouth of the canyon generally appear to be less than several metres thick and are composed of imbricated, wellsorted boulders. The last flood that deposited these boulders is believed to have been a debris torrent with a low content of fines. Mean intermediate diameter decreases from about 1.5 m just beyond the mouth of the canyon, where the channel width expands to 300 m, to about 0.5 m downstream to the point at which the valley is no longer confined on its south side. Using the empirical formula of Costa (1983), these clasts represent velocities decreasing from about 6.5 m s − 1 to 3.7 m s − 1 . Flood velocity and discharge were also calculated within the canyon, using , Costa's (1983) method and by the Manning equation. Parameters for the calculation include a channel width of 65 m, flow depth of 3.5 m (average height of the boulder berm), an average slope of 0.038 and a roughness coefficient of 0.06. The resulting values include a velocity range between 6.8 m s − 1 and 7.3 m s 1 and a corresponding discharge range of ∼1550 m 3 s − 1 to 1660 m 3 s − 1 . A lower limiting discharge of 1320 m 3 s − 1 was obtained with an assumption of critical flow conditions. The boulder fan is much coarser than the older alluvial plain sediment, suggesting an increase in flood magnitudes in more recent timesperhaps in response to renewed uplift of the mountain front and/or climate change. A calibrated rainfall-runoff model was developed using SWAT to estimate modern flood discharges in Wadi Isla. The magnitude of discharge from 1998-2006 did not exceed 500 m 3 s − 1 . Artificial precipitation amounts (90 and 150 mm) were used to extrapolate from recent rainfall amounts to the amount of rainfall needed to produce a discharge range of 1320 m 3 s − 1 to 1660 m 3 s − 1 . Results show that rainfall must range between ∼102 mm and 125 mm to produce this discharge.

Geological Society of America Bulletin, 1987

Glacial-lake outbursts occurred in the northern Great Plains as ice-marginal lakes suddenly drain... more Glacial-lake outbursts occurred in the northern Great Plains as ice-marginal lakes suddenly drained, forming an interconnected system of glacial-lake spillways. The outbursts were highly erosive, and consequently, deposits from such discharges are rare in the spillways. ...

Environmental and Engineering Geoscience, 2007

... Evans, SG, 2002, Contrasting failure behavior of two large landslides in silt and clay: Canad... more ... Evans, SG, 2002, Contrasting failure behavior of two large landslides in silt and clay: Canadian Geotechnical Journal, 39. 46-62. GeoRef. ↵ Griffiths, DV, and Lane, PA, 1999, Slope stability analysis by finite elements: Geotechnique, 49, 3. 387-403. ... Glynn, ME, Chase, RB, and ...

Environmental and Engineering Geoscience, 2008

... the cross-section balancing method produces geometrically permissible results, it is highly i... more ... the cross-section balancing method produces geometrically permissible results, it is highly intuitive and extremely time consuming, especially when dealing with multiple blocks (Chase et al ... The oldest and simplest approach is polynomial interpolation (Kincaid and Cheney, 2002 ...

Boreas, 2013

ABSTRACT Tunnel valleys are common throughout the terrain of the Saginaw Lobe of the Laurentide I... more ABSTRACT Tunnel valleys are common throughout the terrain of the Saginaw Lobe of the Laurentide Ice Sheet in southern Michigan. The set of valleys described in this paper is regularly spaced in a radial pattern behind the Kalamazoo Moraine, an ice-marginal position formed during retreat from the Last Glacial Maximum. These valleys are divided into proximal and distal groups lying north and south, respectively, of a major river valley that cross-cuts the tunnel valleys at right angles. Based on a series of rotasonic borings and core analysis, the proximal valleys are shallow, contain minimal sediment fill, and overlie fine-grained diamicton and glaciolacustrine sediment, whereas the distal valleys are deeply incised into the substrate and are partially filled with coarse sediment. The distal valleys terminate within a broad zone of high-relief, hummocky topography representing stagnation and collapse behind the Kalamazoo ice margin. The proximal valleys occur within a more subdued landscape located farther from the ice margin. Although some elements of existing genetic models are consistent with these valleys, none appears to be completely compatible with their stratigraphy and morphology. Initial incision of the valleys could have involved short-lived moderate- to high-discharge flows, followed by deposition during or after the events. The deep incision and thick, coarse sediment in distal valleys in the stagnant marginal zone probably involved supraglacial meltwater draining to the bed as the margin downwasted. Fining-upward eskers inset into the valleys were formed by flows of declining energy in small late-stage conduits.

ABSTRACT The stable oxygen and hydrogen isotopic composition of fossil groundwater (>30k y... more ABSTRACT The stable oxygen and hydrogen isotopic composition of fossil groundwater (>30k yrs B.P.) over North Africa is progressively depleted from west to east (e.g., average δ18O: Morocco: –6.4‰; Algeria: –8.01‰; Tunisia: –8.38‰; Libya: –8.56‰; and Egypt: –10.98‰) compared to the modern precipitation (e.g., average δ18O ± 1δ: Morocco: –5.46‰ ± 1.22‰; Algeria: –3.9‰ ± 1.19‰; Tunisia: –4.67‰ ± 0.54‰; Libya: –3.8‰ ± 0.44‰; and Egypt: –3.96‰ ± 0.54‰) suggesting that the precipitation during the previous wet climatic periods (450,000 yr B.P to 10,000 yr B.P) resulted from wind regimes different from those prevailing today. The isotopic composition of fossil ground water can be used as a proxy for the isotopic composition of the paleo-precipitation recharging those ground waters with the Atlantic Ocean providing the source of moisture for recharging waters over Northern Africa. Based on this premise, a simple box model can be considered to model the paleo-precipitation to follow a simple Rayleigh distillation. Such a model shows that the reduction vapor factor was up to 30% by the time the moisture bearing air masses reached what is modern day Egypt. This model will be compared with available precipitation data for present day North African sites to constrain atmospheric processes that operated during the Pleistocene over Northern Africa that were responsible for the formation of the fossil aquifers (e.g. Nubian Aquifer) with depleted isotopic ratios.